1. Field of the Invention
The present invention relates to control of letter or text data among a plurality of devices which will make use of that data. The present invention is applicable to a letter data control system, a letter data control method, and to a letter data control device which may form part of that system.
The present invention is particularly, but not exclusively, concerned with the situation where a plurality of work stations are connected to a common printer such as a laser printer.
2. Summary of the Related Art
In document processing or editing, it is now increasingly common to make use of distributed processing, in which various documents are created at a plurality of work stations, and printed at a printer or printers connected to the work stations via a data network forming a transmission path between the work stations and the printer(s). In a basic type of such a system, the printer has a predetermined font, and each work station has to contain font data corresponding to that stored by the printer if the work stations are to display the same result, and/or to print the same results. For languages based on a large number of characters, this means that letter data of many styles and sizes must be stored in each device that is to use the letter data (work station, printer, etc). For example, in the case of Japanese some 7000 characters are used, and therefore must be stored. Therefore, each device that is to use the letter data must have a very large memory, and this is expensive. Furthermore, if new font data is added to the system, or the original font data is changed, every device that is to use the data (work station, printer) has to receive the same new font data.
It is also known to make use of a device known as a file server which is connected to the network between the work stations and the printer. The file server stores centrally a plurality of font files, and the font file needed by each work station and each printer is transmitted via the network to the work station or printer as appropriate. In this way, the memory space of the work stations and printers may be reduced, since they only need to store the font file for the font they are using at any particular time. However, in such a system, the whole of any given font file must be transmitted.
At this stage is is important to distinguish between the term "font file" and the term "letter data". In a conventional file server, the file server cannot analyze the content of a given font file, and must transmit all of that font file. Each font file is divided into letter data and each font file stores a complete set of letter data.
It is also important to appreciate a difference between fonts. It is possible to store letter data i.e. data representing a character in a number of ways. Each of these ways is known as a font, and fonts can be grouped into vector fonts and dot fonts. Dot fonts store the character in the font of a series of dots which are printed by the printer. Dot fonts are easy to use, and permit a high output rate. However, magnification or rotation of the character causes the character shape to be disturbed or broken, and if large letters are needed, they will involve a large number of dots and therefore a large storage capacity is required. Vector fonts, on the other hand, store part of the information. The term "vector fonts" in this specification includes stroke fonts, which record the co-ordinates of key nodes of a character, and information relating to the width of the lines between those codes, line fonts, which record the co-ordinates of the outline of the character, and meta fonts which store only part of a given character, so that a given character is formed by assembling a plurality of letter data from the meta font. Vector fonts have the advantage that they can be magnified or rotated without causing a break in the shape, but are more complicated and therefore produce a slower output. Therefore, if the font used at the printer is a vector font, printing will be slow, whilst if it is a dot font, the quality of the printing may be compromised.